1. Technical Field
The present invention relates to a quantum interference device, an atomic oscillator, an electronic apparatus, and a moving object.
2. Related Art
As an oscillator having high-accuracy oscillation characteristics on a long-term basis, an atomic oscillator is known which oscillates on the basis of energy transfer of atoms of an alkali metal such as rubidium or cesium (for example, see JP-A-2012-191523). In general, an operating principle of the atomic oscillator is classified broadly into a method using a double resonance phenomenon based on light and microwaves and a method using a quantum interference effect (CPT: coherent population trapping) based on two types of light beams having different wavelengths. However, the atomic oscillator using a quantum interference effect can be made smaller than the atomic oscillator using a double resonance phenomenon, and thus has been recently expected to be mounted to various devices.
For example, as disclosed in JP-A-2012-191523, the atomic oscillator using a quantum interference effect includes a gas cell in which gaseous metal atoms are sealed, a light emission unit that irradiates the metal atoms in the gas cell with a laser beam including two types of resonance light beams having different frequencies, a light detection unit that detects the laser beam having passed through the gas cell, and an optical component provided between the light emission unit and the gas cell. In such an atomic oscillator, an electromagnetically induced transparency (EIT) phenomenon occurs in which both of the two types of resonance light beams pass without being absorbed into the metal atoms within the gas cell when a frequency difference between the two types of resonance light beams has a specific value. The photodetector detects an EIT signal which is a sharp signal generated in association with the EIT phenomenon.
In the atomic oscillator disclosed in JP-A-2012-191523, the gas cell and the light detection unit are accommodated in a first package, the light emission unit is accommodated in a second package, and the optical component is accommodated in a third package. The packages are bonded to each other in the order of the first package, the third package, and the second package. The packages are mounted on, for example, a substrate and used in a state where the packages are bonded to each other.
However, in such an atomic oscillator, when the substrate is deformed due to an external force applied thereto, the external force is transmitted to the packages through the substrate. As a result, there is a possibility of a positional deviation of each package, that is, an optical axis deviation of the atomic oscillator occurring. Further, there is a possibility of the temperature of the substrate being changed due to, for example, a change in an environmental temperature or exhaust heat of the light emission unit. In this case, there is a concern that the temperature change may affect the packages on the substrate.